Recoilless firearm and ammunition therefor



April 12, 1949.

w. J. KROEGER ET AL RECOILLESS FIREARM AND AMMUNITION THEREFO R 4 Sheets-Sheet 1 origifi l Filed May 20, 1944 William rlKrneger [Il um-rhea W. MUCSfiEI v iltiomwu April 12, 1949. w. J. KROEGER ET AL RECOILLESS FIREARM AND AMMUNITION THEREFOR 4 SheetsSheet 2 Original Filed May 20, 1944 W1 ll1nm 1L] KruEgE-P BlnrenCEWMuaaen H 92, a. ammflm April 12, 1949. w. J. KROEGER ETAL RECOILLESS FIREARM AND AMMUNITION THEREFOR 4 She ets-Sheet 3 Original Filed May 20., 1944 Willium LT- K'nnger Clarence W. M11659!" April 1949. w J. KROEG-ER ET AL 2,466,714

- EREFOR Original Filed Ma y 2 o 1 9 44 Patented Apr. 12, 1949 UNITED RECOILLESS FIREARM AND AMMUNITION THEREFOR William J. Kroeger and Clarence Walton Musser, Philadelphia, Pa.

Continuation of application Serial No. 536,590, May 20, 1944. This application April 26, 1948,

Serial No. 23,185

25 Claims. (Cl. 89-]..7)

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) The invention described in the following specification and claims may be manufactured and used by or for the Government for governmental purposes without the payment to us of any royalty thereon.

The present application is a continuation of application Serial No. 536,590 filed on May 20, 1944, now abandoned, in the names of William J. Kroeger and C. Walton Musser for "Recoilless firearms, ammunition therefor, and ballistic design thereof.

Our invention relates to firearms of the recoilless type and it has special reference to non-recoil guns wherein the forces of rearward reaction that result from projectile discharge are neutralized by forwardly acting counter forces simultaneously set up by the propellent charges combustion.

Broadly stated, the object of our invention is to improve the design and extend the usefulness of recoilless guns wherein the named recoil neutralization is efiected by a rearward escape of generated powder gas through openings or oriflees in the guns breech.

A more specific object is to lighten the weight and increase the firepower of recoilless weapons of the named open-breech type.

Another object is to evolve for such firearms a quantitative theory of ballistic design plus empirical formulae of proven accuracy.

A further object is to provide improved chamber and breech constructions for such recoilless guns and to make available new and improved ammunition for use therein.

A still further object is to provide improved designs for breech orifice nozzles, to facilitate orifice area adjustment and the securing of zero recoil at a desired performance level, and to neutralize gun twist with rifled barrels.

An additional object is to provide improved means for assuring substantially complete combustion of the powder within the guns chamber, minimizing the blast to the rear, reducing the area which this blast covers, and minimizing rearward discharge of unburned powder and fragments.

A still additional object is to make possible the construction of a one-manrecoilless firearm capable of shooting projectiles carrying considerable quantities of explosive through relatively long distances and yet not exceeding the weight limitations of an infantry weapon.

Other objects and advantages will become apparent as the disclosure and description hereof proceeds.

In constructing one recoilless firearm pursuant to foregoing we: (a) make the guns chamber of substantially larger diameter than the ammunition cartridge case which fits therein; (b) support this cartridge case centrally in this enlarged chamber solely from the cases two ends; (0) provide in the guns breech a rearwardly opening orifice of unique annular nozzle design and with ready adjustment for optimum area; (d) use wall metal for the cartridge case which is perforated throughout the case's length and circumference and which permits discharge of propellent combustion gases radially against the chamber's surrounding wall and thence rearwardly from the gun through the breechs annular orifice; (e) pre-engrave the projectile to permit its more ready passage through the rifled bore of the guns barrel; and (I) so coordinate the breech and firing mechanism as to permit quick and convenient loading and firing.

Our invention itself, together with illustrative embodiments thereof, will best be understood from the following description taken in conjunction with the accompanying drawings wherein:

Fig. 1 is a perspective view of a recoilless gun of 57 millimeter caliber which incorporates our inventive features and which is illustrated in position for firing from the shoulder of a user;

Fig. 2 is a similar showing of the same weapon supported from a tripod and there being aimed by a user;

Figs. 3 and 3A constitute a section on line 3-3 of Fig. 4 giving an enlarged view of the gun of Figs. 1-2 and showing the internal construction of that guns barrel, chamber, breech details, ammunition and firing mechanism;

Fig. 4 represents the breech end of the same gun as viewed from the left of Fig. 3 with the breech block locked in the chamber where it constitutes the inner wall of an annular orifice;

Fig. 5 is a similar showing of the gun with the breech block withdrawn and swung down from the chamber and with the ammunition removed therefrom;

Fig. 6 is a section view on line 6-6 of Fig. 3 showing further details of the breech block and the tappet housing support therefor;

Fig. 7 is a section on line l-l of Fig. 4 through the orifice throat adjusting blocks plus other parts of the guns breech and firing mechanism;

' Fig. 8 is a partial section on line 8-8 of Fig. 4 through the breech block and the turning handles that are afiixed thereto;

Fig. 9 is a section on line 9--9 of Fig. 3 through the guns rifled barrel and the projectiles rotating band;

Fig. 10 is an enlarged section on line llll0 of Fig. 3A through the trigger handles safety button and the hammer's spring retainer and housing;

Fig. 11. is a sectional showing of the cartridge case's front stop shoulder and powder-retaining disc; 1

Figs. 12-13-14 are enlarged showings of the hammer's split safety fixture plus the slotted hammer and hinge housing tubes therearound; Figs. 15-16-17 are further views of the hammer and hinge housing tubes showing the safety lever in three difierent positions;

Figs. 18-19 illustrate a multi-purpose tool userul for assembling and disassembling the weapon;

Fig. 20 shows the recoilless gun's internal construction in simplified schematic form; and

Fig. 21 is a section view on line 2l-2l of Fig. 5

The complete recoilless gun Our inventive improvements are here illustratively disclosed as being incorporated in a military weapon of 57 mm. caliber capable of a completely recoilless firing of projectiles weighing nearly 3 pounds at muzzle velocities of over 1 feet per second. This guns over-all length is only 60.82 inches and its total weight is less than 40 pounds. It is designed for carrying and use by one man and when held in the position shown by Fig. 1 may without danger or discomfort be fired from the user's shoulder with great accuracy and high military'effectiveness; it may also be mounted on a light tripod of the character shown at M in Fig. 2 and there also aimed and discharged with remarkable accuracy and firepower.

As the description proceeds itwill become apparent that our improvements may also be. applied to firearms of sizes, characters and shapes other than the one here disclosed and that the I! (see Figs. 3-4) partially closing (see Fig. 20)

the rear of the chamber; a trigger handle [8 for the user's right hand by which firing of the weapon is controlled; a barrel handle 19 for the user's left hand by which training on the target is aided; and a sight 20 for aiming the gun in conventional manner.

This sight 20 maybe of a telescopic or other type capable of accommodating ranges from a minimum of a small number of yards up to a maximum of about 3000 yards. It may be mounted on the guns barrel in any suitable manner; as directly over the barrels top, as shown in Fig. 2, or sufficiently inclined from that top position to-make aiming more convenient, as indicated by Fig. 1.

As here represented, the gun's trigger and barrel handles l8 and I9 are suitably clamped around the barrel l at the spaced locations shown by Figs. 1-2 and with the angular relation further indicated by Figs. 4-5-6. 7

The barrel, chamber and breech As here shown, the gun's barrel l5 has an] inside diameter of 5'? millimeters. The bore of this barrel is rifiedto securethe usual gains in accuracy and range which a spinning of the projectile in flight makes possible. The rifiing' reprecoilless firearms constructed in accordance with our invention; however, the accuracy and range characteristics'oi smooth-bore barrels are so far inferior to proven performances with rifled barrels that the latter are highly to be preferred for most practical weapons 01' ourimproved nonrecoil type.

As here shown, the gun's chamber l6 takes the form of an enlarged cylinder which isaflixed at its forward end to the rear of barrel ii in any integrally secure manner, as, by the aid of screw threads 21. If desired this connection may be rendered more permanent by. a brazing of metal (not shown) around the entire circumference of the juncture. Such'brazing constitutes a gastight seal whichprevents damage to the threads from powder leakage therethrougmit also prevents relative turning between the barrel and chamber.

As the drawings show, the guns breech block is a spider-like?" element removably secured within the rear end of chamber l6 and consti-- tutes only a partial closure therefor (see Fig. 20). The breech block is actually an apertured supporting member on which are fixed certain vanes 52-53 whose form and function will later be described in detail. It takes the form of a cylindrical block I I which is radially spacedirom the chamber wall in a manner to form a substantially annular orifice or venturi that leads from the chambers interior to the rear exterior of the gun. In Fig. 20 a section of this annular orifice is shown at 22.

Four locking lugs 29 (see Figs. 3-4-5-6) extend radially from this central breech block I] in spider-like" fashion and interfit with mating protrusions 30 (see Figs. 3 and 5) on the chamber wall interior. These mating parts have the form best shown by Fig. 3, and when engaged as in Figs. 3. 4 and 6 they securely lock the breech block l'l within the rear of the chamber.

The chamber wall spaces which circumferentially separate the locking protrusions 30 have a diameter larger. than the maximum for the breech block lugs 29, and this relation enables free longitudinal movementby those lugs through the spaces named. This movement is utilized in inserting the breech block into the chamber and.

also in withdrawing it therei'rom, all in a manner to be described presently.

when insertedand locked within the chamber as shownin Figs. 3-4-6 this breech block I! constitutes a firm support for the ammunition which The complete round of ammunition Cooperating with the barrel, chamber and breech structure just described is ammunition having the unique character shown in Figs. 3, 7 and 11. As here illustrated. the complete round of this ammunition includes a projectile 32 inserted into the rear bore of the barrel IS: a cartridge case 33 communicating with the rear of projectile 32 and centrally supported within the cylindrical chamber l6 by the barrel at the front and by the breech block at the rear; a quantity of propellent powder 34 within the cartridge case; and powder igniting means shown in the form of a primer 35 and booster 36.

As here represented, this ammunition's cartridge case 33 has a diameter which is substantially less than that of the surrounding chamber l6; it being shown as approximately the same as the barrels bore and only about half the chamber diameter. The cartridge case wall preferably is of durable metal, such as steel or brass, or of other material. A prerequisite for the case is that it be of sufficient thickness and strength as to remain intact during firing.

Perforating this wall metal are a large number of relatively small openings 38 distributed throughout substantially the entire length and circumference of the case in the uniform manner indicated. These case wall openings 38 constitute an aggregate area which is nearly V; of the total surface area of the represented cartridge case 33. This aggregate opening area is roughly six times the bore areaof the gun's barrel.

For preventing the propellent powder 34 from falling out of these openings during loading and prior to firing, and for acting as a diaphragm capable ofwithstanding adequate pressures before rupturing, a thin layer of frangible material 39 such as a heavy paper is placed inside the perforated case 33 between the case wall and the powder. Such a lining disintegrates early in the combustion cycle of the propellent powder and thus enables escape of combustion gases and burning powder radially through the openings and into the chamber space immediately surrounding the case.

The unique case construction shown permits the named radial expansion of powder gases into the surrounding chamber without rupture of the metal between wall openings 33 or other damage to the case. In open-breech guns of the type here considered such security against failure of this kind is exceedingly important for were the breech orifice to be blocked by metal or other obstructions recoil neutralization would be violently upset and dangerously high pressures would occur.

The propellent powder represented at 34 substantially fills the entire volume of the cartridge case interior that is behind a forward retaining disc 40 (see Fig. 11). That disc preferably is of frangible material such as cardboard about inch thick. Its purpose is to prevent the propellent powder from occupying the cartridge case in the extreme forward portion where no wall openings are provided and thereby to safeguard the unperforated area of the case wall against rupture upon firing.

We have used conventional double base powders and have found them to exhibit satisfactory burning characteristics at the relatively low chamber pressures employed by recoilless guns of the improved type here disclosed. Typically, such pressures for the particular 57 mm. weapon shown may be of the order of 5000 pounds per square inch.

Such operating pressures are far below those encountered in conventional closed-breech guns where 50,000 pounds per square inch is typical for military rifles and other small arms, and around 30,000 pounds per square inch is characteristic of larger caliber (above 0.60) firearms. As will bepercussion type such as is used in ammunition forcaliber .50 firearms of conventional design. This primer serves to ignite a larger charge of booster explosive 31. By combustion of this booster charge the entire mass of propellent powder 34 is ignited.

Both the primer 35 and the booster 36 are carried by the cartridge case head 4| in the central position shown where the attachment is rendered mechanically secure by force fitting or other suitable expedient. In this position the primer 35 is engageable by a firing pin 42 protruding through the center of the breech block I I and there actuated by firing mechanism later to be described.

In the loaded position shown this cartridge case head 4| is engaged by a mating recess 3| in the breech front. This recess 3| flares outwardly (see Figs. 3 and 8) toward the front more conveniently to receive the case head during loading. By its engagement with the head, the rear of cartridge case 33 is centrally positioned within chamber l5 and the entire case is restrained against backward movement.

A similar central positioning of the forward end of the cartridge case is effected by protrusion of an extreme front section 43 thereof into the bore of barrel i5. Restraining this forward protrusion at the point where the case head 4| snugly fits against breech block I1 is a stop shoulder ring 44 which encircles and is mechanically secured to the forward portion of the case 33, as by a shrink fit of the character indicated in Fig. 11. The front face of this stop ring may either be square for direct contact with the rear of barrel i5 or have the rearward flaring shown.

This ring 44 restrains the cartridge case against longitudinal movement in the forward direction and'thus insures that the case head will at all times hold the primer 35 in proper position for effective engagement by the gun's firing pin '43.

As here shown the ammunitions projectile 32 communicates with the front section 43 of the just described cartridge case and is suitably held therein by the represented force fit overlap connection which permits ready forward release of the projectile upon combustion of the propellent powder. In instances where the projectile may not extend completely back (see Fig. 11) to the cartridge case's stop ring 44, the desired positioning of the powder-retaining disc 40 just ahead of that ring may be maintained by any suitable spacer such as that shown at 45 in Fig. 11.

The represented projectile 32 makes use of a rotating band 46 (see Fig. 3) which is pre-engraved (see Fig. 9) to assure more ready passage of the projectile through the barrel l5's rifled bore. For the 57 mm. weapon here described, that band may satisfactorily be made of brass or other metal (such as gilding) about 34; inch wide, and the pre-engraving thereof preferably is dimensioned to provide with the barrels rifiing a dianietral clearance of the close order of about 0.005 inch. Clearances of this order assure positive k it :and zvienturir Therefore the pressure force's rear-s: area: actinsia ealhsit; obstructions presieiited :hy the: breech can :be counteracted th e iori: war-div acting :pressure forces zaicting on the small i 5; airnula rl filfwaiidi portion: of the chalnibier iii; the? foi' miz'dil yE acting: drag: forces of the roieotne =82 n therifled barrel 1:5 and by the forwardly; acting i registration wlthzthe harrei si rifiinsi pr vent? ob-I 5 i tionabie raw or thesroiectueawhue within? the: bore. and at the instant; or leaving. the gun; and at: he same time permit; the: desired free pas I :s'aeei of f the :proieotiie through the: irified barrel upon; combustion of the propeilent charsaz f f 2 :In zop nebreeah aims: of the: type :here consids cred? such; free passage is exceedingly important oreeicom pon'ent produced :bythe pressure of ex for were :the: projectile: to Zia-m the; :rearwardly :pa'ndlng gases? in the: conical and divergent poir emanating combustion: gases then would exert l tions of the earlier indicated annular; orifice: 22: their fiiil iorward foree on the weapon? itself mesons; 21c: betweien rthe gunis breech block: izI bodily pr pe :it ar army :5 ro k t; psand :the rear we 0 chamber l6: wherein: engraving of theprojectiie: minimize this: goe :bioclc lease-cured. J v 1 2 2 1 2 1 1 i i 2A3isimostcleailyillustratediiyfigs;4- fi 6g this suchprg-igngmving makes m; am o annular orifice extend all% the way: around that ribations to the represented; open-breech we'afp bl cks central: core or huhand is obstructedzonlii as practical performance; :A: eu ttin g bye pm :bythge: four :radialivanesfit-i-eiwhich commenc ectiile or its own: rifting g to es one Q for? a pro s it e ia wm: h c mmon :h hreriioa and tar.

- I niaatcattheiroutward extremiti selling ioiice whichis si bs or; any: increased.

iwhieh raise ts subject Wide variations: in% 21359 been narrow radial width at itsgfront or throat, the sented as including an internal recess for carrying annular orifice flares Dutwardly (see a quantity of high explosive charge (not shown) toward the rear with a total angleof spread of which may be demnated by Suitable means such approximately 15 degrees. The exact value of as a time or other fuse (not shown) installed in this angle is chosen to yield the optimum of forthe Pmjecti1 47 (or base) in wen'klmwn ward force component due to an expansion of manner- Optionally molecule might the powder gases in1passing rearwardly through consist M P 50nd mass of metal m m the orifice as earlier explained. Too narrow an event the illustrated recess for high explosive angle is f und to t down t magnitude of t i would be dispensed with. In either case the axial 50 fbrward force component, while if t angle i and transverse moments of inertia and the dismade too wide the gases seem no longer tokeep tame from the 11056 to W pmlecwe's center J contact with the steepness of wall separation and gravity can be so coordinated will the firing much of the desired nozzle efiect again is lost. Velocity and barrel Iifimg as to assure stability Formaximum effectiveness it would be desirable during fi to'extend the annular orifice to a substantial Yaw observations m de an other firin a axial dimension but practical considerations show ine by us confirm h prolectile 32 that acceptable performance is achieved when the Stabk when fired 5 Illustrated barrel nozzle orifice has the relatively short length which having the represented rifling twist. In order to our drawings indicate (see Figs. 3, 7 and 20). p rmit use of the proj c il s ha n w r 'e t Thus we prefer to select for the nozzle an axial stability characteristics, it is merely necessary to length whi h gives a. rear or discharge area, of increase the twist of barrel rifiing to some steeper approximately four times the orifices front or order. Through a proper coordi at o of the throat area. Dimensions other than that shown tors earlier named our recollless firearm here dismay of cdurse be utilized th varying degrees of closed thus may make satisfactory use of projecrelative fl ti ness tiles of a wide variety of forms types and shapes In our achievement of complete neutralization The annular orifice and adjustable nozzle of recoil we find that there exists an optimum Recoilless firearms of the open-breech type here ratio between the area of the gun and the considered neutralize the forces of rearward rethroat area of the breech Orifice- This ratio is action by forwardly acting counter forces. In dependent Primarily the ammmt 0f expanur improved. weapun these counter forces are 81011 obtained in the venturi 22 and. t0 a 185561 produced by acceleration of the rearwardly esextent upon such factors as the relative weights caping generated powder gases with an accomof the powder and projectile. In a firearm o! penying pressure gradient within the chamber the annular orifice type here disclosed this ratio saryadjustment these blocks 63 do not alter thebasic nozzle shape thereof, and hence they constitute a particularly eflicient means of effecting the required adjustment.

The maximum throat area is of course realized- I when both blocks 63 are removed; hence the annular orifice is designed to afford a throat area large enough to meet the maximum requirements under that condition. Applying the figures earlier stated, this might give a bore-area -to throat-area ratio of the 1.35 lower limit. To change this ratio to its other extreme of the named 1.70 maximum,

it is merely necessary to install at 63 orifice blocks of size sufiicient to cut down the total throat area by the requisite amount; and to obtain ratios of intermediate values there may be substituted adlusting blocks 63 of varying intermediate size.

In practice we find it convenient to mark on each block the particular value of bore to throat area ratio which its use (along with a companion block of the same dimension) will give. Thus, one set of blocks will be marked 1.58; another 1.60; a third 1.62; and so on.

Choice of the exactblock size is most effectively determined by trial firings in a pendulum or other gun suspension which is free to swing and thereby indicate the presence, direction and magnitude of recoil should same exist. In the illustrative 57 mm. weapon represented, zero recoil is found to require the use of a pair of blocks which give a bore area to throat area ratio of the order of 1.60. With such adjustment the nozzle throat has a total area which is approximately one tenth of the cartridge case's perforation area. 1 Y

Neutralization of rotational reaction Firearms with rifled barrels experience a rotational reaction by virtue of the spinning motion that firing imparts to the projectile. In the particular gun shown barrel I5s right hand twist gives clockwise rotation to projectile 32 upon forward movement thereof through the barrel, and this right-hand acceleration of the projectiles mass imparts counterclockwise torque of equal magnitude to the barrel.

Our improved weapon includes provision for neutralizing such reactive torque by causing the explosive gases which rearwardly discharge through the annularbreech orifice 22 to impart to the weapon counterbalancing torque of the same magnitude as that which the rifled barrel imparts to the projectile. This provision is effected by so specially shaping the rear tailpieces of the breech block vanes 5253 that the gases passing through orifice 22 have angular momentum imparted thereto.

Each of these breech block vane tailpieces tapers in the general manner shown by Fig. 27 from a maximum cross section beneath locking lug 29 (see Figs. 3-5) rearwardly toward a minimum and much narrower width at the rear extreme for m recoil will lie within the range of about thereof (see Figs.4-5-6). If this-taper were the same on both sides of each tailpiece, the discharge of powder gases there past would exert no rotative force in either direction, but instead the side force components set up by the expanding ases would be the same in both directions and hence completely counteract one another.

To obtain the desired torqueneutralization we modify the tailpiece fiaring to the extent indicated by Figs. 4-5-6 and 27. There it can be seen that the angle on the one side of each tailpiece diifers from the angle on the other side in the proper amount and direction to give the gases a counteracting spin about the gun axis. The eflect is to impart to the axes of breech orifice openings 22 small angular displacements (all in the same rotative sense) with respect to the main axis of the gun's barrel I5 and chamber Hi.

In consequence the sides of these vanes having the smallest angle have imparted thereto a stronger side or tangential thrust from the expanding gases than do theopposite vane sides, and there thus is imparted to the breech block a torque counteracting that applied by the projectile. Only the relatively small degree of angular unbalance indicated is found sufiicient to I make the thus imparted torque of the same I magnitude as the barrel l5 imparts to the projectile 32 in advancing it through the rifled bore.

During firing the breech block I! transmits this neutralizing torque to the chamber and thence to the barrel, and in this way all forces of rotational reaction are neutralized in a very simple yet highly eifective manner. In the illustrative weapon shown the combustion gases that flow rearwardly through breech orifice openings 22 have imparted thereto a counterclockwise spin which is opposite to the clockwise spin given by the gun's right hand rifiing to the forwardly fired projectile 32. As the vane structure of the nozzleforming portion of the breech block I! is asymmetric in relation to the gun's axis for each venturi opening, a difierent amount of expansion tends to occur for opposite sides of each venturi for axial gas fiow. Therefore, the center line of the gas fiow through each nozzle is tangentially diverted in a circular pattern about the axis of the gun. The accompanying gas reaction torque exerted on the gun is clockwise and thus neutralizes the counterclockwise projectile reaction torque-received by the barrel l5.

Were the gun barrel to be rified with a left hand twist rotational reaction could be neutralized in exactly the same way merely by shaping the breech vanes in the opposite sense.

The breech block carrier and lock mechanism Explanation has already been given of how the breech block I1 is secured in the rear of chamber i6 by the aid of that blocks locking lugs 29 and the mating protrusions 30 on the chamber interior. In the locked position represented by Figs. 3, 4 and 6, this support is all that is needed to hold the breech block in place, and it is fully adequate to restrain the maximum chamber pressures which combustion of the propellent charge 34 sets up.

To facilitate loading, and removal'of the cartridge case 33 after firing, provision is made for unlocking this, breech block ll, rearwardly withdrawing it from the chamber l6 and swinging it out of alignment with the chamber interior to some downward position such as that shown in Fig. 5. Aiding these actions is an operating member which illustratively takes the form of a pair 11 of handles 43 which protrude from'the breech block. a radial support member shownin the form of a tappet housing ill which extends into that block's center, and a lateral support member shown in the form of a hinge housing (see Fig.3) whichinterconnects the radial member tance somewhat greater (see Fig. 3) than do the remaining two breech block vanes 53 (see Fig. 5). By these handles an operator may rotate the breech block through the small angular distance indicated at d in Fig. 6. In the gun here shown h block continues to receive support twist, then the locked position of the breech block should of course be at its counterclockwise limit this range of angular movementis of the order withdrawal is the radially disposed tappet housing ill earlier mentioned. This housing is attached at its outer end to a pivot tube or hammer housing sleeve 56 sliding and turning in the stationary hinge housing or support tube 5| earlier mentioned as being fixed to the outside of chamber it; from this attachment the radial tappet housing extends through a cut away portion in a rear rim 5'! (see Fig. 6) of the breech block to that block's center where the gun's firing pin 42 is mounted (see Fig. 3) i There circular openings in the front and rear .of this radial member Bil accommodate opposing bosses 53 and 53 (see Fig. 3) projecting from the breech block and from a cover plate 60 therefor. This cover plate is secured to the block by the aid of three bolts 6| which pass through the plate and into tapped openings in the block metal thereby holding the plate firmly in a mating recess in the block's rear rim 51.

The rotatable connection thus established permits the earlier named angular movement of the breech block ll with respect to the chamber l6, and also with respect to the tappet housing which extends into the block's center from the chambers outside. In this way application of clockwise turning force tohandles 49 effects looking of breech lugs 29 behind the mating protrusions 30 of chamber l6; and application of counterclockwise turning force disengages those lugs from the chamber protrusions and thus frees the breech block for rearward withdrawal from the chamber. Both of these turning movements are sented (by Figs. 4-5-6) opening I 05 in the wall of the rear breech rim 51. g

' In a weapon having the represented right hand rifling, the gas forcesapplied as earlier explained to neutralize torque reaction exert clockwise turning effort on the breech block and thereby maintain the locked position thereof during firing. were the gun to be rifled with left hand limited in their extent by the sides of the repreof turning movement. t a

The earlier named hinge housing sleeve 51 is secured to the outer wall of chamber j it; (see Fig. 3) bybrazing or other permanent :iorm of attachment. This hinge housing is continued forwardly to the trigger handle l8 (see Figs. 12-3-3A) and within it the smaller diameter hammer housing sleeve 56. is carried (see Figs. 15-16-17) in a manner permitting both radial and lengthwise movement. This form of carriage permits the aflixed tap pet housing 50 (see Fig. 3) to be withdrawn rearwardly with respect to the hinge housing II; and also. to be rotated with respect thereto.

Once. therefore, the breech block H has been disengaged from the chamber protrusions 30,

I applicationof rearward force to handles 49 causes the breech block ll, tappet housing 50 and hammer housing 58 all simultaneously to be moved back awayfrom the rear of chamber It. The range of this backward movement is sufllcient to allow complete clearanceof the breech block with respect tothe chamber. andwhen this condition is realized the breech block and tappet housing may both be swung downwardly to the position shown in Fig. 5. l l

7 Here the entire interior area of the chamber i6 is unobstructed in a way permitting ready insertion of the projectile and cartridge case 32-43 into the gun orreadywithdrawal of a fired cartridge case from the gim's chamber.

To reinsert the breech block into the chamber 4 it is merely necessary to swing the tappet housing 50 clockwise and upwardly about its hinge mounting in housing 5| position the breech block in its counterclockwise limitof travel with respect to housing 50; thrust the so petitioned breech block forwardlyinto the open end of chamber l6; and finally turn the breech block to its clockwise limitfof rotationin which the locking lugs 23 thereof engage with the chambers mating protrusions (see Fig. 3). j

Close fitting of the radial tappet housing 50 against the end of the hinge housing 5| when'the breech block I1 is locked within the gun's chamber may be secured in any desired manner such as 2 117 the aid of shims of the type shown at 66 in The firing mechanism For igniting 1 the ammunitions propellent charge 34 at the will of an operator, use may be made of any suitable tiring mechanism either electrical (not shown) or mechanical (here disclosed). Here represented by way of illustration is a unique mechanical type of firing mechanism by the aid of which an operator may fire the weapon by a simple. squeezing of the trigger handle II. In the disclosed arrangement the firing pin 42 carriedby the gun's" breech block I! (see Fig. 3) receives through a tappet 81 a thing blow created by the rearward movement of a rodshaped hammer 68. The force incident to this rearward movement originates in a compression spring 63 and is made available for flringthe sun when a trigger HI protruding from the front of trigger handle I! is depressed.

The just named tappet 81 (see Figs. 3 and 6) is mounted on a rocker pin 1 I within the radially disposed tappethousing 50. As earlier described this radial member 50 also constitutes the support for the breech block i I when withdrawn from the weapon's chamber l8; serving to close the 13 housings back is a removable cover 18 held in place by an overlapping of the breech block cover plate 60.- A tappet retractor spring 14 urges the outer end of this tappet to the forward travel limit shown in Fig. 3, and in that condition the inner end of the tappet is separated from the rear of firing pin 42 by the substantial clearance which Fig. '3 also shows.

The illustrated hammer 68 takes the form of a long, slender rod of steel or other suitable metal slidably contained (see Figs 15-16-17) within the housing sleeve 56 earlier described as constituting a support (see Fig. 3) for the outer end of the radial tappet'housing 58. As earlier explained,

this housing sleeve or pivot tube 56 is rotatably and slidably contained within the outer hinge housing tube 5|, which hinge housing is fixed (as by brazing) to the outside of chamber l6. That hinge housing, in turn, extends from the weapons chamber to and slightly past the trigger handle l8 where the forward end thereof is closed by a plug 18.

From Figs. 3-3A (and. Figs. 15-16-17) it will be seen that the companion hammer housing 56 likewise extends within the stationary hinge housing 5| from the rear location of tappet housing 50 to the forward location of trigger handle l8. Here the housing or pivot tube 56 terminates in a spring retainer 16, taking the form of the represented sleeve (see Fig. 3A) attached to the tube end by a thread connection..

Figs. 15-16-17 show that the inside diameter of this hammer housing 58 is somewhat larger than the outside diameter of the hammer rod 68 which it surrounds, and the earlier named hammer spring 69 is carried (see Figs. 3-3A) within the space thus made available. The forward end of this hammer spring abuts against the retainer 16, while the rear end of' the spring exerts force against a spacer sleeve 11 (see Figs. 15-16) also slidably carried between the central hammer 68 and the housing sleeve 56 which surrounds it.

Adjacent to this spacer 11 on the side opposite to the spring is a reduced diameter section of the hammer 68 and surrounding it is a split safety fixture made up of two parts 1988 having the mating character shown in Fig. 12. These'two parts are housed within the hammer tube 56 for restricted slidable and rotative movement, and they also permit the hammer 68 to move axially therethrough along the hammers reduced diameter portion.

Radially protruding from part 19 is a safety arm 8| which extends through registering slots 62 and 55 in the concentrically disposed hammer and hinge housings 56 and 5|, respectively (see Figs. 3, 15-16-17) to theoutside for manipulation by the operator. The named slots 62 and 55 have the character illustratively shown in enlarged Figs. 13-14, and during cooking and firing of the hammer rod 68 these slots cooperate with the safety arm 8| in a manner to be explained presently.

The slot 55 in the outer or hinge housing 5| (see Fig. 13) has .the substantial width later named and is of length greater than the axial distance through which the hammer 68 and safety arm 9| move during cocking and firing. The cooperating slot 62 in hammer housing 56 is comprised of two parts identified as 62A and 823 (see Fig. 14). This slot 82 is wide at its front 62A and narrow at its rear 623 and has on the narrow side thereof a total length somewhat greater than that of housing 5|s slot 55; the wide region of this hammer housing slot is sufiiciently long to enable thesaiety fixtures 19-80 to be inserted therethrough for assembly around the reduced diameter portion of hammer 68.

This hinge housing slot 55 (see Fig. 13) and the hammer. housing slot 62 at its widest section (see Fig. 14) both have a total circumferential width of somewhat more than 90 degrees. In cooperation with safety arm 8| these two slots serve to restrain the downward swinging movement of the tappet housing 58 (see Fig. 5) to an angle of only slightly more than that 90-degree limit.

Under the after loading" conditions reprehousing 5|.

cocked to the forward position where a latch head 83 thereof is advanced past trig er 'llls sear 84; the hammer spring 69 .is compressed between hammer housing 56s forward retainer 16 and the rearward spacer 11; that spacer abuts parts 19-80 and through them is held against rearward movement by engagement of safety arm 8| with the hammer housing 56's short lower recess (see Figs. 14 and 15); and in consequence the hammer 68 has none of the springs compressive force exerted thereon.

To arm the hammer in readiness for firing, the safety. arm 8| must be pushed forward against the compression of spring 69 to clear the recess 12 of the short slot 62A in tube 56 (see Fig. 14) and rotated upwardly into alignment with hammer housing 56's long slot 623 as shown in Fig. 16. This permits the spring 69 and spacer 11 to push the safety fixture 19-88 backward to the point where the rear thereof abuts the larger diameter of the hammer 68. That hammer now receives the rearward force of the spring and pulls latch head (see Fig. 3A) 83 against the trigger sear 84.

Under these conditions a depression of the trigger 16 will release the hammer allowing the compressed spring rapidly to move it backwardly along with spacer 11 and the safety fixture. By this movement the safety arrm 8| moves in the narrow slot 623 of housing tube 56 to the rear l mit thereof. This rear or as fired limit of the safety lever is shown by Fig. 17.

It is reached just before the end of hammer 68 has contacted tappet 61, and at that point the springs compressive force is removed from the hammer. The momentum of acquired motion causes the hammer to continue to move back through safety fixture 19-80 and by striking the outer end of tappet 61 to impart a blow to the firing pin 42 and thereby detonate primer 35.

To recock the hammer in preparation for the firing of another round, the breech block I1 is by counterclockwise rotation disengaged from the chamber l6 and rearwardly withdrawn by handles 49. Tappet housing 58 transmits this rearward movement to the hammer, housing 56 and pulls retainer 16 backward in the stationary hinge Safety arm 8|, now abuttng (see Fig. 13) the rear of hinge housing 5|s slots 55, restrains the spacer 11 from rearward movement, and in consequence, the hammer spring 69 now becomes compressed.

By this rearward movement the narrow slot 623 in hammer housing 56 is drawn past the safety arm 8| and to a position of housing 56 where that safety arm is in the area of housing 56s wide forward slot 62A. Incident thereto is a complete clearance of the breech block I! from the end of chamber l6, and a resultant freedom of swinging movement of this block downwardly to the position shown in Fig. 5.

Such a swinging of tappet housing 58 rotates the hammer housing 56 counterclockwise in the scription started.

spasms stationary hinge; housing 6!. During this rotation of this hammer housing 58 the safety arm 8! continues to abut the: rear "of hinge housing ls slot 55, as showndotted by Fig. 13, and thus the recess 12 in the short slot 82A of housing 56 I (see Fig. 14) is brought into alignment with that arm. Release of breech block withdrawing force now allows the hammer spring 68 to pull the hammer housing 88 forward and thus re-engage this housing's short slot 62A recess with arm II, as shown byFig. 14. t a

. Subsequent swinging of the breech blockxand tappet housing 80 upwardly (clockwise) into alignment with the weapons chamber rotates housing tube 88 and safety arm 8| 7 clockwise in the stationary hinge housing 6!. Here the breech block may be forwardly re-lnserted into the end of chamber 18 by movement which carries hammer housing 56, safety arm 8i and the compressed spring 88 all forward inthe stationaryhinge tube 8i. I I

By this forward movement the firing mechanism is returned tothe original or after loading" condition ofFlgs. 3 and 15 with'which this d Firing pin, loaders and trigger safeties position pulling of the trigger 10 is ineffective for releasing the hammer,

weapon is possible. 7

Before the weapon can be tired, it is necessary for the loader ofthe gunto push safety arm 8| forward out of housing tube its'slot recess (see Figs. 14-15) and rotate it counterclockwise into alignmentwith that tubes long narrow slot 828,

thus effecting the armed" position of Fig. 16.

When that has been done the compressive force of hammer spring 89 is transferred to the trigger sear 84, and withdrawal thereof from the latch head 88 allows the hammer to fly backwardly and cause tappet 61 to impart a percussive blow to the firing pin 42.

In addition to this loaders safety, our improved weapon here disclosed also includes: (a) a trigger. safety; and (b) a firing pin safety.

The trigger safety utilizes mechanism associated with the trigger Ill within the trigger handle l8. This trigger is mounted for rotation about a support point 86 (see Fig. 3A), and theilower portion of the trigger is held forwardly by a leaf spring 81. This spring urges sear 84 upwardly into engagement with the hammers latch head 88 The trigger handle l8 comprises two sections fastened to a carrier member 84 which is fixedly mounted on barrel i5. Also carried by the trigger handle I8 is a trigger guard 89, which completely surrounds the exposed portion of trigger 10 and requires that pulling movement be imparted to the trigger through application to this guard. A fastening ferrule 80 for this guard is borne by the carrier member 94 (see Figs. 3 and 10) slightly below the corresponding support 88 for the trigger.

16 button terminates in a locking key '82 and is held in the extendedpositlon represented by a trigger safety spring 93 supported in compression by a hollow screw 85. r I

As shown in Fig. .10, thlslocklng key 92 fits into mating slots in one side of the trigger guard 89 and is prevented from rotational motion by fitting into the slots in the stationary central plate 84 of thetrigger handle. As long as the safety buttonal protrudesirom the side of handle it, as showninFlg. 10, spring 93 holds half of this non-rotatinglocklng key 82. in the slots in the guard side. Underjthis condition the guard is locked against rearward movement into contact with trigger 18,.and application of pressure to the guard 89 is prevented from eflecting trigger operation.

When, however, the safety button 9iv is depressed the locking key 82 is moved completely movement and application of pressure thereto and no firing of the.

.bythe weapon's breech block 11.

then becomes effective for pulling the trigger and firing the weapon; In view of the fact thatthe safety spring. is continuously actin as afore- {said to move the safety button 91 into the "safe" "position; the button must be kept depressed by the gunner during the entire time it is desired to keep trigger guard 89 free for actuation of the trigger; p

The thirdor firing pin'form of safety involves the hammerjtappet 61 and engagement oi? the inner end thereof'with the firing pin 42 carried Surrounding the end of. this firing pin (see Figs. 3 and 8) is I the rearward :boss. 58, earlier described as fitting The trigger safety feature is dependent on this guard 89 and utilizes the mechanism illustrated by Fig. 10. There the trigger guard 89 is shown as having two sides which pivot around ferrule 80. This ferrule is hollow and protruding from one end thereof is a safety button 9 l This safety into a mating opening in the inner end of the tappet housing 50.

Inorder that the tappetil may strike the firing pin, this circular boss 58 is provldedwith the slot best represented in Fig. 8. When properly aligned with the tappet this slot permits such forward movement thereof as is necessary to impart a detonating blow to the firing pin.

This proper alignment (see Fig. '7) exists only when the breech block I1 is locked within chamher It by clockwise rotation of lugs 29 behind the chamber's mating protrusions 30. When the breech block's lugs are disengaged from the chamher, this breech boss 58 is rotated to a position where the described slot therein no longer aligns with the tappet, and under this condition the boss wall mechanically blocks advancement of the tappet into contact with the firing; pin.

Hence, even though the breech block ll may be inserted into the chamber it is possible to fire the weapon only after there has been imparted to that block sufllcient clockwise rotation to effect secure locking in the firing position.

Other mechanical details I wedge a member to be turned into a cooperating recess I02 in the tool's body.

By this one tool the following five operations can be performed: ,(a) the gun's breech cap bolts 9| (see Figs. 4 and 7 can be turned by inserting wrench end 91 into the mating recesses'in the bolt heads; (b) the guns orifice block bolts .64

"(see Figs. 5 and 7;) can be turned by similarly inserting, wrench end 98 into corresponding bolt head recesses; v(c) the gun's. trigger handle screw ,95 (see Fig. 10) can be turned by engaging screw driver blade 99 with the slotted head thereof;

(d) the gunshinge housing plug" (see Fi 3A) .canbe turned by a fwedge? engagement. thereof ,between knurled disc i0! and the opposing side of the tool's recess I02; and (e) the gun's spring retainer 16 (see Fig. 3A) can (after removal of plug .10 and withdrawal of hammer 60lbe turned by inserting the tools small diameter end 99 into the retainers center and bringing wing extensions l00; into engagement with cooperating slots (not shown) in the retainers end face.

' The smallness and lightness of this multipurpose tool allows it readily to be carried by the gun operator for immediate availability at all times. i

. Loading and firing I 'From the foregoing it will be seen that we have provided an improved recoilless firearm which offers special advantages in connection with both loading and'firing. To place the ammunition round within the weapon it is merely necessary to unlock the breech block l'l, withdraw it from chamber I6 and swingit downwardly to the position shown in Fig. 5, thus completely freeing the chamber opening.

assay 33 remains intact during this firing and is not ruptured or otherwise damaged. Indications are that the pressure within the chamber 16 on the inside and outside of the cartridge case wall equalizes itself early during the burning cycle. Thus, after the case has been fired some of the openings 38 may be found to have thin films of ash either partially or completely covering their area.

Subsequent withdrawal of the fired cartridge case from the chamber is eifected by unlocking the breech block, withdrawing it rearwardly and The ammunition round is now inserted into the opened chamber and the rear of the barrels bore. As the projectile enters the barrel, the lands on the pre-engraved band 6 are brought into alignment with the grooves of the barrel bore, and forward thrust is then continued until the shoulder ring 44 at the cartridge case front abuts with the barrels end. In this position the projectile 32 imparts centering support to the entire cartridge case 33 and allows the rear head ll thereof to droop only slightly from the rear chamber center. I

The breech block 11 is now moved forwardly into the chamber. In approaching and engage ing'with the cartridge case head 4|, the flared recess-in the breech block's front serves tocenter the head thereby constituting a second support for the cartridge case. Clockwise rotation of the breech block by handles 49 now locks it into the chamber with the front shoulder ring in abutment with the barrel and the case head ll in abutment with the breech block, the primer 35 in alignment with the firing pin 42 and the entire cartridge case 33 centrally positioned within the surrounding chamber l-G.

The weapon is now ready for firing, and upon the earlier explained presettin g of safety arm BI ruptures the frangible layer 39 and produces radial expulsion" of the explosive gases into the chamber 16'. This expulsion starts early in the burning cycle and is accompanied by. continued combustionofthe powder. i

. dividual soldier an efiective defense and offense swinging it downwardly out of register with the chamber. This frees the fired case for ready withdrawal from the chamber and conditions the weapon for insertion and subsequent firing of another ammunition round.

Performance data The firing of hundreds of rounds of ammunitionhas confirmed beyond all doubt the success- 1 ful and practical character of the improved recoilless firearm here disclosed. For example, in. tests where the represented projectile 32 which was used has a weight of between 2.5 and 3. pounds, by use of the proper'propellent charge muzzle velocities in excess of 1200 feet per second were consistently attained.

Complete neutralization of recoil is uniformly achieved, and when firing the weapon from the shoulder users reportacomplete absence of weapon motion backward, rotative, sidewise or forward. The same, of'course, holds true when the weapon is fired from a. tripod as shown in Fig. 2.

Accuracies of a high order also are. achieved. At 300 yards it is possible to hit a one-foot bull'seye with remarkable consistence; at 600 yards the shot pattern area is well defined by a 13-foot circle; and at 1000 yards hits can be scored on a 6-foot target. Accuracies of comparable order are realized'at 1500 and 2000 yards, and high ef-..

fectiveness of the weapon is. found to continue even upto3000 yards.

The relatively light weight and small'dimensions of the weapon at once make it possible for infantry use and place in the hands of them-- the projectile out of the barrel, minimum appor-.

tionment of the total propellent charge energy to the recoil neutralizing rear blast, and marked .pleted; due to the rapid expansion and cooling of the gases as they continue to drive the Projectile through the bore. This is a very emcient process and results in the conversion of as high as of the internal energy ofthe powdergas to projectile kinetic energit, l

In an open-breech recoilless gun the pressure, after burning has ended, falls not only due to the forward motion of the projectile but also because of the very considerable amount of gas issuing from the breech. It turns out, therefore, that a recoilless gun, projectile and powder charge combination designed for completionof powder combustion at the momentof projectile exit from the muzzle is onlyslightly less efiicient than the same combination with an equal charge of a fast- 20 nozzle and have more eflliciently securedzero recoil at a desired performance level; that we have assured substantiallyi complete combustion of the powder within thegun's chamber and thereby er powder which would operate at a higher pressure and which would give some expansion of the gases after burning ends. i

For in the latter case, although a higher pressure peak is obtained and the powder combustion is completed earlier, just as in the conventional gun, much of the benefit of the consequent gas expansion behind the moving projectile is lost. This is because the nozzle discharge .be-

comes more effective asthe gas temperature falls, andthe driving pressure thus is lowered more rapidly than would be the case during the corresponding. gas expansion in a conventional gun.

In our analysis of the physical mechanism of the recoilless gun and its application to design, we consequently have concentrated upon the objective of obtaining the best possible gun powder combustion completed at theinstant of projectile exit from the muzzle. This results in a pressuretravelcharacteristic which, when graphically illustrated, has an essentially fiat shape and offering what we have found to be the best solution of the weight problem.

Summary The earlier described qualities of superior recoilless gun performance are the direct result of our here disclosed inventive improvements in the design and construction of open-breech firearms. The individual features of such improvement are numerous, and in the complete weapon these fea-' tures efl'ect the named results throughcooperation and interaction which are both unique and novel.

Our disclosed arrangement and correlation of recoilless firearm components is not believed to have been either sug ested or used heretofore, and although we are aware that certain of the individual elements of our improved weapon may have existed in other environments yet it has remained for us to perceive their advantageous interacting possibilities and to correlate them in a wholly new and unexpected manner which yields the superior performance results already set that we have provided improved chamber and breech constructions for such recoilless guns and have made available new and improved ammunition for use therein; that we have facilitated the construction and adjustment of breech orifice ,minimized the blast to the rear and accompany ing discharge of unburned powder and fragments;

and that we have made possible the construction of a practical Jone-man recoilless firearm capable of shooting projectiles of substantial size through relatively long distancesand yet not exceedingthe weight limitationsof an infantry weapon. I 1 l Our inventive improvements thus are capable of wide application and hence are not to be restricted to the specific form here shown and described by way of illustration. i

.1. In a recoilless firearm, the combination of a barrel, a chamber communicating therewith, an amrnnuition round comprising a projectile positioned in the rear bore of said'barrel and a cartridge case within said chamber communicating with said projectile and containing propcllent powder, a metal wallfor said case forming for said powder a cylindrical enclosure of diameter substantially less than that of the surrounding chamber so as ,toleave 'suflicient spacebetween said case wall and surrounding chamber for radial expansion of powder combustion gases through selected wall areaportions which constitute a supporting said cartridge case in spaced relation,

to the chamber wall therearound.

2. In a recoilless firearm, the combination of a barrel, a chamber communicating therewith, an ammunition round comprising a projectile positioned in the rearbore ofsaid barrel and a cartridge case containing propellent powder positioned. within said chamber and communicating with said projectile, a metal wall for said case forming for said powder a cylindrical enclosure of diameter substantially less than that of the surrounding chamber and being perforated by a relatively large number of openings distributed throughout the circumference and length thereof, a breech block so constructed and so mounted in the rear ofsaid chamber as to support said cartridge case in spaced relation to the chamber terior thereof, meansfor igniting said, powder whereby to discharge said? projectileforwardly out of said barrel and at the same time expel throughsaid case wall openingsradially into said chamber and thence rearwardlyout of said orifice powder combustion gases which neutralize. the forces of, recoil.

[3. In a recoilless firearmgthi e combination of a barrelya chamber communicating therewith, an

ammunition round comprising a projectile positioned in the rear bore of said barrel. and a car.- tridge case containing propellent powder positioned-within said chamber and communicating with said projectile, a metal wall for said case forming for said powder"a cylindrical enclosure of diameter substantially less than thatflofthe surrounding chamberandlbeing perforated by a relatively large number ofopenings distributed throughout the circumference and len th theretion of the powder, and a breech block in the rear of said chamber there supporting said cartridge case in spaced relation to the chamber walls and there also providing, an orifice which leads from the chambers interior tothe rear'exterior thereof and which permits escape of powder gases in proper quantity and at proper rate to neutralize recoil.

4. In a recoilless firearm, the combination of a barrel, a chamber communicating therewith, an ammunition round comprisin a projectile positioned in the rear bore of said barrel and a cartridge case positioned within said chamber communicating with said projectile and containing propellent powder, a metal wall for said case forming for said powder a cylindrical enclosure of diameter substantially less than that of the surrounding chamber and being perforated by a relatively large number of openings distributed throughout the circumference and length there! of, a layer of frangible material separating said powder from and preventing its passage through.

the case wall perforations prior to firing but yielding to the as pressure of powder combustion, a breech block secured in the rear of said chamber and there providing an orifice which leads from the chambers interior to the rear exterior thereof and which permits escape of powder gases in proper quantity and at proper rate to neutralize recoil, and means including said breech block for supporting said cartridge case in spaced relation to the chamber wall therearound.

pellent powder positioned within said chamber and communicating with said projectile, a metal wall for said case forming for said powder a ey 1 lindrical enclosure of diameter substantially less than that of the surrounding chamber so as to leave sufficient space between said case wall and said surrounding chamber for radial expansion of powder combustion gases through selected wall area portions which constitute a substantial percentage of the total case wall area, and a breech block in the rear of said chamber there supporting said cartridge casein spaced relation to the chamber walls and there also providing an orifice which leads from the chambers interior to the rear exterior thereof and which permits escape of powder gases in proper quantity and at proper rate to neutralize recoil.

8. In a non-recoil gun, the combination of a barrel having a rifled bore, a chamber communicating with said barrel, an ammunition round comprising a projectile positioned in the rear of said bore having a rotating band pre-engraved to match the bores rifling and being dimensioned for free forward movement through the barrel ficient space between .said case wall and said 5. In a non-recoil gun, the combination of a barrel, a chamber communicating therewith; an ammunition round comprising a projectile positioned in the rear bore of said barrel and a cylindrical cartridge case having a perforated metal wall positioned within said chamber communicating with said projectile and having a diameter substantially less than that of said chamber, propellent powder within said cartridge case, a breech block secured in the rear of said chamber in radially spaced relation to the chamber wall and there forming with that wall a sub-- stantially annular orifice leading from the chambers interior to the rear exterior thereof, and

, means including said breech block for supporting said perforated cartridge case in spaced relation to the chamber wall therearound.

6. In a non-recoil gun, the combination of a barrel, a chamber communicating therewith, an ammunition round comprising a projectile positioned in the rear bore of said barrel and a cylindrical cartridge case having a perforated metal wall within said chamber communicating with said projectile and having a diameter substantially less than that of said chamber, propellant powder within said cartridge case, a breech block secured in the rear of said chamber and there providing a rearwardly diverging orifice which leads from the chambers interior to the rear exterior thereof and which upon combustion of said powder and discharge of said projectile permits rearward escape of powder gases in proper quantity and at proper rate to neutralize recoil, and means including said breech block for supporting said perforated cartridge case in spaced relation to the chamber wall therearound.

7. In a recoilless firearm, the combination of a barrel, a chamber communicating therewith and having an internal diameter substantially'greater than that of the barrel, an ammunition round comprising a. projectile positioned in the rear bore of said barrel and a cartridge case containing prosurrounding chamber for radial expansion of powder combustion gases through selected wall area portions, and a breech block in the rear of said chamber there supporting said cartridge case in spaced relation to the chamber walls and there also providing an orifice which .leads from the chambers interior to the rear exterior thereof and which permits escape of powder combustion gases in proper quantity and at proper rate to neutralize recoil.

'9. In a recoilless firearm, the combination of a barrel having a rifled bore, a chamber communicating with said barrel, an ammunition round comprising a projectile positioned in the rear of said bore having a rotating band pre-engraved to match the bores rifling and being dimensioned for free forward movement through the barrel and a cartridge case containing propellent powder positioned within said chamber and communicating with said projectile, a metal wall for said case forming-for said powder a cylindrical enclosure of diameter substantially less than that of the surrounding chamber and being perforated by a relatively large number of openings distributed throughout the circumference and length thereof, a breech block in the rear of said chamber there supporting said cartridge case in spaced relation to the chamber walls and there also providing an orifice which leads from the chambers interior to the rear exterior thereof, and means for igniting said powder whereby to discharge said projectile forwardly out of said rifled barrel and at the same time expel through said case wall perforations radially into said chamber and thence rearwardly out of said breech orifice powder combustion gases which neutralize the forces of recoil.

10. In a non-recoil gun, the combination .of a barrel having'a bore rifled with twist in a given directionfachamber secured to the rear of said barrel havingfthe periphery of its internal wall sii'rface 'i iut 'iaway at spaced portions to provide a substantiallyiannular orifice interrupted by locking protmsions that extend substantially radially I large number of openings distributed throughout bores rifling, a metal wall for said case forming for said charge a cylindrical enclosure of diameter substantially less than that of the surrounding chamber and'being perforated by a relatively large number of openings distributed throughout the circumference and length thereof, a breech block in the rearward portion of said chamber having itsperiphery cut away at spaced portions circumferentially of the'block 'to'provide'a, substantially annular orifice interrupted by vanes that extend substantially radially from the for said charge a. cylindrical enclosure of diameter substantially less than that of the surrounding chamber and being perforated by a relatively the circumference and length thereof,'a breech block in the rearward portion of said chamber having its periphery cut away at spaced portions circumferentially' of the block'to' provide a substantially annular orifice interrupted by vanes that extend substantially radially from the V blocks central portion and that cooperate with said locking 'protrusionswithin said chamber to securethe block within the chamber, and rearrotative forces substantially equal to theiforces of block's central portion and that cooperate with said locking protrusions within said chamber to secure the breech block within the chamber, and

means including said' vanes for 'causingthe said combustion gases which pass. rearwardly through v v said annular orifice to impart to said breech block and chamber given-direction rotative forces substantially equal to the forces of twistfwhich said .projectil'e receives from said rifled barrel.

11. In a non-recoil gun, the combinatio oi a barrel having a bore rifiedwith twist in a given direction. a chamber securedto the rear of said barrel having the periphery of its internal wall. surfacecut away at-spaced portions to provide a substantially annular orifice'interrupted by lock:

ing protrusions that extend substantially radially I inward from the chambersinner wall toward its central cavity, an ammunition round comprising a projectile positioned in said barrels rear bore, a propellent charge for: generating combustion gases by which said projectile is pushed forwardly through said barrel and rotated in said given direction by said boresrifiing, a metal wall for said case forming for said charge a cylindrical enclosure of diameter substantially less than that of the surrounding chamber and being perforated by a relatively large number of openings distributed throughout the circumference and length thereof, a breech block in the rearward portion of said chamber having its periphery cut away at spaced portions circumferentially of the block to provide a substantially annular orifice interrupted by vanes that extend substantially radially from the blocks central portion and that cooperate with said locking protrusions Within said chamber to secure the block within the chamber,

and sidewalls for said vanes so flared axially as to receive from the said combustion gases which pass rearwardly through said annular ori fice given-direction rotative forces substantially equal to the forces of twist which said projectile receives from said rifled barrel.

12. In a non-recoil gun, the combination of a barrel having a bore rifled with twist in a given direction, a chamber secured to the rear of said barrel having the periphery of its internal wall surface cut away at spaced portions to provide a substantially annular orifice interrupted by locking protrusions that extend substantially radially inward from the chambers inner wall toward its central cavity, an ammunition round comprising a projectile positioned in said barrels rear bore and a cartridge case containing a propellant charge for generating combustion gases by which said projectile is pushed forwardly through said barrel and rotated in said given direction by said bore's rifling, a metal wall for said case forming wardly extending side walls for said vanes axially flared by unequal angles on opposing sides to receive from the said combustion gases which pass through said annular'orific'e given-direction twist which said projectile receives from said rifled barrel. I

13. Ina non-recoil, gun, the combination of a barrel, a chamber communicating with said barrel, a breech'block movableinto and out of the rearward portion of said chamber and having its periphery cut away'at spaced portions circumferentially of the block to provide a substantially annular orifice interrupted by vanes extending substantially radially from the central portion of the block, and enacting interlocking members I formed on the peripheralportions of said vanes and the inner wall of said chamber.

14. In a non-recoil gun, the combination of a barrel, a chamber communicating withsaid barrel, a breech block operable'ior movement into and out of the rearward portion of said chamber I for lockingengagement therewith and having its periphery cut away at spaced portions circumferentially of the block to provide a substantially I annular orifice interrupted by vanes, extending substantially radially from the central portion of the block, coacting interlocking members formed on the peripheral portions of said vanes and the inner wall of said chamber, and a breech block operating member carried by oneof said vanes and usable for moving the breech block into and out of locking engagement with said chamber. a

15. In a non-recoil gun, the combination of a barrel, a chamber communicating with said barrel, a breech block movable into and out of the rearward portion of said chamber and having its periphery cut away at spaced portions circumferentially of the block to provide a substantially annular orifice interrupted by vanes extending substantially radially from the central portion of the block, coacting interlocking members formed on theperipheral portions of said vanes and the inner wall of said chamber, a cartridge case of cross sectional area substantially less than that of said chamber supported adjacent its forward end in said barrel and having its side walls perforated, and means carried by the forward portion of said breech block to support the rearward portion of said cartridge case in spaced relation to the chamber wall, said substantially annular orifice connecting the annular space between the cartridge case and chamber wall with the outside atmosphere.

16. In a non-recoil gun, the combination'of a barrel, a chamber communicating with said barrel, a breech block movable into and out of the rearward portion of said chamber and having its periphery cut away at spaced portions circumferentially of the block to provide a substantially annular orifice interrupted byvanes extending substantially radially from the central portion of the block, and coacting interlocking members formed on the peripheral portions of said vanes and the inner wall of said chamber, the breech block walls of said annular orifice and the adjacent walls of said chamber diverging rearwardly to produce a rearwardly flared annular opening of nozzle shape.

17. In a non-recoil gun, the combination of a barrel, a chamber communicating with said barrel, a breech block movable into and out of the rearward portion of said chamber and having its periphery cut away at spaced portions circumferentially of the block to provide a substantially annular orifice interrupted by vanes extending substantially radially from the central portion of the block, coacting interlocking members'formed on the peripheral portions of said vanes and the inner wall of said chamber, and adjustable means usable for selectively varying the e'fiective cross sectional area of said annular orifice in order to accomplish substantial elimination of all recoil from the gun notwithstanding dimensional changes to the breech block or chamber caused by use of the gun.

18. In a non-recoil gun, the combination of a barrel, a chamber communicating with said barrel, a breech block movable into and out of the rearward portion of said chamber and having its periphery cut away at spaced portions circumferentially of the block to provide a substantially annular orifice interrupted by vanes extending substantially radially from the central portion of the block, and coacting interlocking members formed on the peripheral portions of said vanes and the inner wall of said chamber, the block walls-of said annular orifice and the adjacent walls of said chamber diverging rearwardly to produce a rearwardly flared annular opening of nozzle shape, and adjustable means selectively usable to maintain uniform the effective cross sectional area of said rearwardly diverging orifice without altering the nozzle shape thereof notwithstanding dimensional changes to the breech block or chamber caused by use of the gun.

19. In a non-recoil gun, the combination of a barrel, a chamber communicating with said barrel, 9. breech block movable into and out of the rearward portion of said chamber and having its periphery cut away at spaced portions circumferentially of the block to provide'a substantially annual orifice interrupted by vanes extending substantially radially from the central portion of the block, coacting interlocking members formed on the peripheral portions of said vanes and the inner wall of said chamber, and an orifice area adjusting member of preselected cross section amxed to said breech block in one of said circumferentially cut away portions thereof whereby to reduce the total orifice area by the amount of said preselected cross section.

- 20. In a non-recoil gun, the combination of a barrel, a chamber communicating with said barrel, a breech block movable into and out of said chamber and having its periphery cut away at spaced portions circumferentially of the block to provide a substantially annular oriflce interrupted by vanes extending substantially radially from the central portion of the block, coacting interlocking members formed on the peripheral portions of said vanes and the inner wall of said chamber and being engageable and disengageable upon locking and unlocking rotations of the breech block within the chamber. a support to:

said breech block disposed exteriorly of said chamber, a companion member rotatively and slideably engaging said support for movement longitudinally of said chamber and barrel, and means extending radially and operatively connecting said breech block to the supports said companion member and disposed in line with one of said vanes in the breech blocks locked position.

21. In a recoilless firearm, the combination of a barrel, a chamber communicating therewith, a breech block movable into and out of said chamber and having its periphery cut away at spaced portions circumferentially of the block to provide a substantially annular orifice interrupted by vanes extending substantially radially from the central portion of the block, a support tube secured to the outside of the chamber and extending lengthwise thereof, a pivot tube within said support tube carried thereby and free to slide and turn with respect thereto, radial means operatively connecting said breech block to said pivot tube, a firing pin in said breech block, a tappet lever carried by said radial means and extending across said annular orifice between the axis of said firing pin and the axis of said pivot tube, and a hammer disposed within the pivot tube and movable axially thereof to engage said tappet lever and operate the firing pin.

22. In a non-recoil firearm comprising a rifled barrel in conjunction with a rear breech portion having an opening for rearward passage of propellent gases, the combination of means associated with said breech portion for converting the translatory motion of said rearwardly moving gases into a rotative force which opposes the forces of twist that are imparted to the firearm upon the firing of a projectile through said rifled barrel.

23. A rifled recoilless gun comprising a breech portion having an opening for rearward passage of propellent gases anda vane structure connected with said breech portion and so positioned with respect to said opening as to convert the translatory motion of said rearwardly moving gases into a rotative force which opposes the torque exerted upon therified gun when a projectile is forwardly fired therefrom.

24. In a non-recoil gun comprising a rifled barrel in conjunction with a rear tubular portion having an opening for rearward passage of propellent gases, the combination of means including vanes so related to said opening that when a projectile is forwardly fired through said rifled barrel those vanes cause the accompanying rearwardly moving explosive gases to impart to the gun rotative forces substantially equal but opposite in direction to the forces of twist which the accelerating projectile exerts upon the rifled barrel.

25. In a recoilless gun having a casing provided with a pressure developing chamber and a coaxial exhaust passage leading therefrom to the rear exterior thereof, a spider-like member removably' fixed within said chamber, said member having a hub portion coaxial with said chamber and a plurality of integral vanes angularly disposed relative to the axis of and extending from said hub portion toward the walls of said chamber whereby to deflect and give a circular motion to gases exhausted axially through said exhaust passage.

WILLIAM J. KROEGER. CLARENCE WALTON MUSSER.

No references cited. 

